The Fluorescence sensing technique for trace detection of High Energy Materials (HEMs) has gained more attention in recent times. In the present paper, the interaction between the fluorophore and HEMs is studied using spectroscopic and electrochemical techniques. The fluorophore polyaniline (PANI) was functionalised by doping it with benzenesulfonic acid (BSA) to increase the processability, and mobility of p-electrons along with decreased p-stacking. It is observed that upon doping the solubility of BSA-PANI is increased, facilitating a higher quenching by commercial explosives, i.e., RDX, CL-20, CL-20:RDX cocrystal. The interaction studies undertaken though fluorescence quenching, FTIR and Resonance Raman studies shows that the benzenoid unit, polaron and bipolaron nitrogen in BSA-PANI interact with nitro groups of HEMs and form a charge-transfer complex between HEMs and BSA-PANI undergoing predominantly a PET mechanism. LOD value is found to be least for Cocrystal (1.876 9 10 -5 M) when compared to other HEMs 3.191 9 10 -5 M (CL-20), 5.904 9 10 -5 M (RDX), 3.734 9 10 -5 M (PETN) indicating that cocrystal can be detected in trace level. The collaborative study between cyclic voltammetry and

Background: Detection of explosives (Nitroaromatic compounds) is one of the major issues faced in global security and to date remains a challenge even though some materials are developed for their detection. This study introduces the use of polyvinylpyrrolidone (PVP), a non-conjugated conducting polymer as a potential fluorophore for sensing nitroaromatics. The stimuli - response of fluorescence of PVP on interaction with energetic nitroaromatics was investigated in the present study. Methods: Fluorescence quenching studies of 5% PVP was carried out by the addition of varying concentration of quenchers (m-dinitrobenzene, trinitrobenzene and 2,4,6-trinitrophenol). To study the effect of different solvents on fluorescence quenching, two different solvents were used i.e., water and ethanol. The quenching studies of PVP with dinitrobenzene and trinitrobenzene was carried out in ethanol and 2,4,6-trinitrophenol was carried out in water. Results: The maximum emission peak intensity of PVP was observed at 445nm in ethanol and 420nm in water which was quenched upon gradual addition of quenchers. This shift in maximum peak intensity of PVP was understood from the change in the solvent polarity. UV-Visible and FT-IR studies were also carried out to understand the nature of interaction taking place between the quenchers and PVP. The limit of detection (LOD) was observed as 1.8x10-3M, 2.5x10--6M, and 3.9x10-6 M for picric acid, dinitrobenzene andtrinitrobenzene respectively. Conclusion: The results envisage PVP as a potential candidate for sensing energetic nitroaromatics with good sensitivity.

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Conducting polymers (CPs) have contributed significantly to the field of sensing. The sensing of nitroaromatic compounds by fluorescence has recently gained more attention due to its sensitivity and selectivity. In this study, polyaniline (PANI) was functionalized by forming a polyaniline-Ag (PANI-Ag) composite and used as a fluorophore for sensing. The nitro groups present in nitroaromatic compounds (NACs) such as 2,4,6-trinitrophenol (picric acid-TNP) and Dinitrobenzene (DNB) act as electron-accepting molecules and quench the fluorescence of polymer chains by showing an amplified quenching effect in which trace amounts of electron-accepting NACs quench emissions of several fluorophore units. The PANI-Ag composite synthesized by interfacial polymerization was analyzed using UV-vis spectroscopy and Fourier-transform infrared (FTIR) spectroscopy for determination of molecular structure; X-ray powder diffraction (XRD) and scanning electron microscopy (SEM/EDAX) for its morphology, which is cubic crystalline silver; and thermogravimetric analysis (TGA) for the thermal stability. The fluorescence quenching mechanism was deduced from the Stern–Volmer plot. The quenching constant value (Ksv) obtained from the Stern–Volmer (S–V) plot was found to be Ksv = 0.1037 × 106 M−1 (TNP) and Ksv = 0.161 × 104 M−1 (DNB). The plot shows a single mechanism with formation of an exciplex complex for TNP with a photoinduced electron transfer (PET) mechanism. The limit of detection (LOD) is found to be TNP = 5.58 × 10−7 M, whereas DNB = 23.30 × 10−6 M shows that the PANI-Ag composite is a potential fluorophore for sensing of nitroaromatic compounds in trace levels.

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